How Does Seakeeper Gyroscopic Stabilization Work?

Seakeeper gyros are becoming more and more popular on sportfishing boats of all sizes – but how the heck do these things work?

Whether you’re on a 30 foot center console or a 60-foot convertible, Seakeeper gyroscopic stabilization truly seems like magic. You flip a switch and – POOF! – the boat stops rolling almost entirely. In fact, we’ve been on several boats both small and large and found a roll reduction of about 90 percent is the norm. How in the world is this possible?

This illustration might be a bit simplistic, but it’s accurate – we’ve found a roll reduction of about 90 percent in both open center consoles, and big convertibles.

Gyroscopic Stabilization in a Nutshell

Although you don’t have to be a rocket scientist to understand how it works, Seakeeper uses a form of technology known as a “control moment gyroscope,” which was quite literally developed for and by rocket scientists. Skylab was the first spacecraft to be outfitted with the system, they’ve been used on a slew of Russian spacecraft, and there are four on the International Space Station alone.

To wrap your head around how control moment gyros work, you first need to look at the different pieces-parts.

Okay: so, how do these things work their magic? Look at the above picture, which we’ve marked up with arrows. Take note of the round orb in the middle, with the red arrow pointing to it. This houses a flywheel, which spins in a vacuum. Next notice the hydraulic arm with the green arrow. This tilts the orb on a gimbal, in reaction to the boat’s movement. Finally, the blue arrows point to mounting spots; the entire affair is securely mounted to the structure of the boat and ties into its stringers and/or bulkheads.

Since the flywheel spins in a vacuum and the unit is cooled with a glycol/seawater system, it can go fast – really fast, up to around 10,700 rpm and at over 550 mph, on some models. This naturally produces angular momentum. That momentum creates torque, which counteracts force – in this case, the force of a boat’s rolling motion. As the boat rocks the hydraulic arms tilt the orb fore and aft, which delivers the torque to port and starboard. Seakeeper calls this “Active Control,” and as one might expect, it’s computer-controlled. The unit’s digital brain monitors each roll cycle, and constantly adjusts the orb’s attitude to best counteract the boat’s roll.

Here’s what the Seakeeper’s parts and pieces look like, in a cut-away view.

An easy way to think of the forces being applied is to picture a spinning top. As long as it spins quickly, momentum and the force it creates keeps it upright. It doesn’t succumb to gravity and fall over until it slows down, or an outside force interferes. Similarly, the force created by spinning flywheel fights against the force of the boat’s lateral movement. Except that in this case it always spins at a controlled rate, and the unit can adjust its attitude to apply more or less force in either direction, as necessary according to the sea conditions and the motion of the boat.

Seakeeper isn’t the first control moment gyro to be designed for boats, but it the most effective we’ve seen yet, and by a long shot. In fact, about 15 years ago (several years before Seakeepers were invented) we were able to measure a 35 percent roll reduction in a Bertram 630 equipped with a marine control moment gyroscopic stabilizer. The difference? Since its flywheel didn’t spin in a cooled vacuum, it couldn’t turn as fast nor produce as much torque. Still, the phenomenon of pressing a button and feeling the boat roll less was quite impressive and at the time, we felt the results were spectacular. The results of the modern Seakeepers is simply that much more impressive.

Here’s another phenomenon we’ve seen time and again: someone on the boat who has never experienced the effects of a Seakeeper before spends time on a boat with one, and at some point asks if it can be turned off so he or she can feel the difference. This happened when we were aboard a 62’ Viking, and again while fishing offshore on the Grady-White Canyon 456.

In both cases, the exact same thing happened – within about 30 seconds of the unit being deactivated the boat was rocking and rolling so much that the same person who made the request immediately asked for it to be turned right back on.

Downsides to Having a Seakeeper

This will be a short section, people, because there really aren’t very many. In fact, the only down-side we can ID is that these things aren’t incredibly cheap. You can usually plan on spending, on average, about five percent of the cost of the boat on a retrofit. On new boats which have designed in a spot for one, and with small units like the Seakeeper 2 (designed for boats under 27 to 32 feet in length) you’re looking at a hair under $25,000 and up. When retrofitting, however, you’ll also have to account for some time lost when the boat’s out of the water and un-usable.

You should also consider the fact that you’ll lose some stowage space, or in some cases, may have to sacrifice something like a cooler or a livewell that may otherwise be built into the spot a Seakeeper would go. Beyond that there’s not much to beef about. We should note that it does take a while for the unit to spool up (usually between 20 and 40 minutes), and that since the bow still goes up and down, the effects feel much more dramatic at trolling speeds or adrift than they do when cruising – though the effect is still far beyond merely being noticeable, at all speeds.

This Seakeeper demo Contender 35 is just one of the boats we’ve taken into the open Atlantic. On all of them, the results have been utterly spectacular.

The bottom line? After spending many days on the ocean on a number of different boats with Seakeepers keeping them steady, you won’t care to ask how a Seakeeper works in the first place. You’ll simply enjoy the magical experience of standing on the deck of a boat that barely rocks and rolls at all, regardless of the sea conditions.

Lenny Rudow …has been a writer and editor in the marine field for over two decades, and has authored seven books. He is currently the Angler in Chief at Rudow's FishTalk Magazine, is Electronics and Fishing Editor for BoatUS Magazine, and is a contributing editor to several other publications. His writing has resulted in 45 BWI writing contest and two OWAA Excellence in Craft awards. Volunteer positions have included NMMA Innovations Award judging, serving as president of Boating Writers International, and serving as the president of the Maryland Freshwater Foundation. Rudow is an alumnus of St. Mary’s College of Maryland, Westlawn Institute of Marine Technology, and The Sea School. He boats and fishes as often as possible on the Chesapeake Bay and in the Atlantic Ocean.